Brain Chip Lets Paralysed Monkeys Walk Again

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Two
monkeys, each with a paralysed leg, were
able to walk again days after spinal injury – all thanks to a wireless,
implantable brain chip system, a study reported in Nature has
shown.

Known
as the “brain-spine interface”, the technology lets brain signals skip a
damaged section of the spinal cord by being beamed to a recording device, then
a computer, and finally to a pulse generator implanted in the lower spine to
activate the legs.

It
was developed in an international collaboration of researchers led by Grégoire
Courtine from the Swiss Federal Institute of Technology in Lausanne who has had
previous success restoring mobility to paralysed rats. But it's the first time
neurotechnology has brought back movement in paralysed primates.

Walking
seems like one of the most natural movements in the world, but it starts with a
highly coordinated set of signals from the brain down the spinal cord to the
lumbar region, which is responsible for activating legs. If the spinal cord
about the lumbar is damaged, it can interrupt those signals.

So
to see if these signals could bypass a spinal cord injury above the lumbar
area, Courtine and colleagues gave rhesus monkeys a lesion near the middle of
their spine. This meant one leg was paralysed.

Close-up of the pulse generator

A
pill-sized implant, made of almost 100 tiny electrodes, was inserted into the
monkeys’ motor cortex – the small part of the brain that sends signals telling
our muscles to move. The implant transmitted brain signals to a recording
device, which relayed the information wirelessly and in real time to a
computer. Algorithms decoded the signals and extracted the message to move –
called a motor state – from the brain activity.

The
motor states were then translated into spine stimulation protocols, which, in
turn, triggered a pulse generator implanted in the spine's lumbar region to get
leg muscles moving. Study co-author Marco Capogrosso, also from the Swiss
Federal Institute of Technology, says at first he wasn't optimistic about it
working but “looked on in disbelief” when the first primate tested began moving
its “paralysed” leg.

“All
the science that we built to get there, all the problem solving and the
technological solutions that we had to put together, all the systems that we
integrated were just working smoothly all together at the same time,” he says.

“Locomotion
may look simpler to achieve than grasping because it is patterned and
repetitive,” he says. "However, in reality, it is not."

Within
a week after the device was switched on, one of the monkeys regained some
mobility without training, walking on the treadmill at a comfortable pace. The
other monkey had a more damaging injury and took two weeks to reach the same
point. The brain-spine interface uses components that have been approved for
research in humans. But there are still some challenges and limitations in the
system to overcome, and it will take several years for the technology to be
fully available to humans.

For
instance, the monkeys could only walk as far as the wireless connection would
allow. In the researchers' set-up, this was less than five metres. Capogrosso
says the researchers aim to embed the computer functions into another chip for
a fully implantable system – or to a smaller device such as a smartphone.